Hand Anatomy and Functions

Hand Anatomy

• Anatomist and Co-Leader: Dr. Redir T Hassan, co-leader of the MSK module and Phase 1 leader at the College of Medicine, University of Duhok.

Hand Objectives

• Objective 15: Understanding, explaining, and demonstrating movements of forearm muscles (extrinsic and intrinsic).
• Objective 18: Identifying and locating major nerves, their distribution (motor and sensory - dermatomes), and consequences of injuries.
• Objective 19: Describing principal arteries and veins of the upper limb, locating arterial pulses and sites for venipuncture/transfusion.
• Objective 24: Identifying superficial structures (tendons, blood vessels, nerves) at the wrist and their injury consequences.

Hand Bones

• Phalanges (fingers): Distal, middle, proximal.
• Metacarpals (palm): Bones numbered 1-5.
• Carpals (wrist): Hamate, Pisiform, Triquetrum, Lunate, Scaphoid, Capitate, Trapezium, Trapezoid (in order from anatomical position).
• Radius and Ulna: Forearm bones.

Flexor Retinaculum

• Description: Thickening of deep fascia, holding long flexor tendons in position at the wrist.
• Attachments: Medially to the pisiform and hamate bones, laterally to the scaphoid tubercle and trapezium bones.

Structures Passing Deep to Flexor Retinaculum

• Lateral to Medial: Flexor digitorum superficialis tendons, median nerve, flexor pollicis longus tendon, flexor carpi radialis tendon.

Structures Passing Superficial to Flexor Retinaculum

• Lateral to Medial: Ulnar nerve, ulnar artery, palmar cutaneous branch of ulnar nerve, palmar longus tendon, palmar cutaneous branch of the median nerve.

Carpal Tunnel

• Description: Fibro-osseous canal anteriorly at the wrist, formed by a deep arch of carpal bones and the flexor retinaculum.
• Contents: Tendons of FDS, FDP, FPL and the median nerve.

Hand Muscles (Groups)

• A. Extrinsic Muscles: Originate outside the hand and insert into hand bones (e.g., FDS, FDP).
• B. Intrinsic Muscles: Five groups within the hand – Thenar eminence (Opponens pollicis, Flexor pollicis brevis, Abductor pollicis brevis), Hypothenar eminence (Opponens digiti minimi, Abductor digiti minimi, Flexor digiti minimi brevis),interossei (dorsal and palmar). lumbricals muscles.

Thenar Eminence

• Description: Prominent swelling on the lateral side of the palm at the base of the thumb.
• Muscles: Opponens pollicis, flexor pollicis brevis, abductor pollicis brevis.
• Innervation: Recurrent branch of median nerve.

Adductor Pollicis

• Origin: Two heads (transverse and oblique) from metacarpals 3, 2 and 3.
• Insertion: Medial side of proximal phalanx of thumb.
• Function: Adduction of thumb.
• Innervation: Deep branch of ulnar nerve.

Hypothenar Eminence

• Location: Base of little finger.
• Muscles: Opponens digiti minimi, abductor digiti minimi, flexor digiti minimi brevis
• Innervation: Deep branch of ulnar nerve.

Interosseous Muscles

• Description: Between metacarpals, inserted into proximal phalanges of each digit.
• Types: Dorsal interossei (abduction), palmar interossei (adduction).
• Innervation: Deep branch of ulnar nerve.

Lumbrical Muscles

• Description: Worm-like muscles associated with each finger.
• Origin: Tendons of flexor digitorum profundus in the palm
• Innervation: Medial two – deep branch of ulnar nerve; Lateral two – digital branches of the median nerve.
• Action: Flex MPJ and extend IPJ.

Blood Vessels of the Hand

• Arteries: Radial artery (thumb and lateral index finger), ulnar artery (remaining digits and medial index finger). Interconnected arches (superficial and deep).
• Veins: Deep veins follow arteries. Superficial veins drain into a dorsal venous network over metacarpals. Cephalic and Basilic veins are main superficial veins.

Nerves of the Hand

• Ulnar nerve innervates all intrinsic hand muscles except the three thenar muscles and two lateral lumbricals, which are innervated by median nerve.
• Radial nerve innervates skin on the dorsolateral side of the hand.

Extensor Retinaculum

• Description: Strong, fibrous band extending across the posterior wrist.
• Attachments: Laterally to the anterior radius border and medially to the triquetral and pisiform bones.